metaphyseal chondrodysplasia, dwarfism, bowing of the long bone, with neutropenia, defective immunity, hypoplastic anemia, and Hirschsprung disease and increased apoptosis of T cell with altered expression of FAS and FAS1, with great clinical variability

hair fine, sparse and light-colored, with an abnormally small caliber on microscopic examination, major immunologic defect that was manifested, for example, as an unusual susceptibility to chickenpox (cases of fatal varicella pneumonia )

substantially high risk of non-Hodgkin lymphoma and basal cell carcinoma at young age

the milder skeletal phenotypes are caused either by two mutations leading to mild-to-intermediate functional alteration of mRNA and rRNA cleavage or by compound heterozygosity with one of the mutations leading to mild-to-intermediate functional alteration and one allele reducing the transcription level by alterations within the distance between the TATA box and the transcription start site